1. Field of the Invention
The invention pertains to the field of toy guns that generate bursts of air to function. More particularly, the invention pertains to improvements in aiming accuracy and to safety of the toy guns and targets for use with these guns.
2. Description of Related Art
Conventional toy guns that shoot solid projectiles (for example, plastic balls) can be dangerous, and both these guns and guns that shoot water are unsuitable for indoor use in ordinary living areas where they may damage furniture and other household items.
Toy guns that shoot air provide fewer personal injury risks and can be suitable for indoor use. For example, U.S. Pat. No. 4,157,703 to Brown et al. (1979) shows a toy gun, in which an elastic diaphragm is deflected by an impulsive force produced by a trigger mechanism, producing a burst of air that can be used to knock down small targets at short range.
A different class of toy air gun generates vortex rings of air. Unlike air blasts from the Brown et al. device, vortex rings are interesting objects in and of themselves. They are highly stable and can travel great distances from their sources while maintaining their shape and intensity before dissipating. Vortex rings are localized disturbances in the air that propagate through the air with a well-defined speed. When the vortex rings strike an object they exert a brief impulsive force due to their forward motion and the rapidly circulating air within them. Consequently, they behave very much like solid projectiles, but without their associated risks.
Toy guns for producing vortices in air have been patented. U.S. Pat. No. 1,473,178 to W. R. Dray (1923) describes a gun in which a flexible diaphragm is retracted by hand and then released, blowing air out a cylindrical tube. This design is very similar to that of the “AirZooka” currently marketed by Zero Toys of Concord, Mass. U.S. Pat. No. 2,534,398 to Beathan (1950) describes a vortex gun with a spring-loaded diaphragm and a circular aperture. U.S. Pat. No. 2,543,651 to Weiss (1951) uses a piston to strike a flexible membrane and force air out a circular aperture. U.S. Pat. No. 2,614,551 to Shelton (1952) describes several configurations of a toy vortex gun, generally consisting of a flexible or rigid diaphragm and mechanisms for displacing it to shoot a burst of air through a circular aperture. U.S. Pat. No. 2,879,759 to Webb (1959) describes a variant on Shelton's basic designs. These guns have their own dangers, including the possibility of objects placed in the barrel being projected out, and of excessive pressure causing damage to, e.g., ears if the output opening is blocked. Other examples include U.S. Pat. No. 1,611,533 by Kirsten (1926); U.S. Pat. No. 1,926,585 by Gibbons (1933), U.S. Pat. No. 2,846,996 to Drynan (1958), U.S. Pat. No. 3,117,567 to Allen (1964), U.S. Pat. No. 3,342,171 to Ryan et al., (1967), U.S. Pat. No. 3,465,741 to Daniel et al. (1969), and U.S. Pat. No. 3,884,471 to Maurer et al. (1975).
U.S. Pat. No. 4,157,703 to Brown et al. (1979) describes safety features for toy air guns. A grid placed in front of the air-displacing member prevents objects placed inside the gun from being projected outward. A vented auxiliary parabolic cone on the outlet of the gun, whose outlet diameter is approximately equal to the diameter of the muzzle opening, provides pressure relief in the event that the outlet of the gun is blocked by, e.g., a child's ear. However both the positioning and patterning of the protective grid, the shape of the auxiliary cone, and the diameter of its opening are such as to dramatically reduce vorticity at the gun's output and the power of the vortex rings it produces, so that this design is a conventional air gun rather than a vortex ring gun. (This is in fact evident from the patent, which states the gun produces puffs of air and makes no mention of vortex rings.) This gun is also designed for relatively short-range targets (up to 8 feet), where airflow at the target will have a large non-vortex component so that the “projectile”-like behavior of any vortex ring is obscured.
Targets for toy air guns have been discussed in U.S. Pat. No. 1,473,178 to Dray (1923), U.S. Pat. No. 1,926,585 to Gibbons (1933), U.S. Pat. No. 2,534,398 to Beathan (1950), U.S. Pat. No. 2,614,551 to Shelton (1952), U.S. Pat. No. 3,884,471 to Maurer et al. (1975), and Des. 259,335 to Gillespie (1981). None of these targets are particularly interesting or entertaining, especially when compared with target-type activities possible with guns that shoot solid projectiles.
U.S. Pat. No. 2,628,450 to Shelton (1953) describes a variant on the vortex gun, which fills the chamber with smoke, so as to render the vortex visible (a smoke ring gun.) Subsequent patents for smoke ring guns include U.S. Pat. No. 2,855,714 to Thomas (1958), A very similar device described in U.S. Pat. No. 6,421,502 B1 to Aronie et al. (2002) is currently marketed as the “Zero Blaster” by Zero Toys. A disadvantage to smoke ring guns is that the air exit velocity and thus the vorticity and vortex velocity must be small; otherwise, the particulates cannot follow the vortex ring's motion and the “smoke ring” disappears. Consequently, they are unsuitable for target-type activities where an appreciable impulse must be delivered to the target to register a hit. Another disadvantage is that the materials used to make the rings visible are all irritants and many are toxic.
A major deficiency of all of these air guns is that they are extremely difficult to accurately aim. Unlike conventional toy guns, relatively large barrel diameters and air collimating or vortex producing apertures (typically 6–12 inches and 2 inches, respectively) are required to produce the strong air displacements and/or strong vortex rings capable of producing visible effects on targets at significant distances. Aiming sights placed on the outside of the barrel are far from the gun's axis, and the parallax between the sight line and the air burst/vortex ring trajectory and resulting aiming errors are large at all target distances, especially at larger distances where the air motion is due almost entirely to the moving vortex ring and where the striking, projectile-like behavior of the vortex ring is most apparent. Deviations in motion of the air-displacing membrane or piston from perfect cylindrical symmetry about the bore axis (as in, e.g., the AirZooka) also produces aiming errors and irreproducibility in air puff/vortex ring strength. No doubt it is for this reason that the commercially marketed vortex gun AirZooka doesn't include targets, and that earlier commercial air gun products included only very large, curtain-like targets that were easy to hit.